The silicon (Si) integrated circuit (IC) has dominated electronics and has helped it grow to become one of the world's largest and most critical industries over the past thirty-five years. However, because of a combination of physical and economic reasons, the miniaturization that has accompanied the growth of Si ICs is reaching its limit. The present scale of devices is on the order of tenths of micrometers. New solutions are being proposed to take electronics to ever smaller levels; such current solutions are directed to constructing nanometer scale devices.
Prior proposed solutions to the problem of constructing nanometer scale devices have involved (1) the utilization of extremely fine scale lithography using X-rays, electron, ions, scanning probes, or stamping to define the device components; (2) direct writing of the device components by electrons, ions, or scanning probes; or (3) the direct chemical synthesis and linking of components with covalent bonds. The major problem with (1) is that the wafer on which the devices are built must be aligned to within a fraction of a nanometer in at least two dimensions for several successive stages of lithography, followed by etching or deposition to build the devices. This level of control will be extremely expensive to implement. The major problem with (2) is that it is a serial process, and direct writing a wafer full of complex devices, each containing trillions of components, could well require many years. Finally, the problem with (3) is that the only known chemical analogues of high information content circuits are proteins and DNA, which both have extremely complex and, to date, unpredictable secondary and tertiary structures that causes them to twist into helices, fold into sheets, and form other complex 3D structures that will have a significant and usually deleterious effect on their desired electrical properties as well as make interfacing them to the outside world impossible.
The present inventors have developed new approaches to nanometer-scale devices, comprising crossed nano-scale wires that are joined at their intersecting junctions with bi-stable molecules, as disclosed and in application Ser. No. 09/282,767, filed on even date herewith. Wires, such as silicon, carbon and/or metal, are formed in two dimensional arrays. A bi-stable molecule, such as rotaxane, pseudo-rotaxane, or catenane, is formed at each intersection of a pair of wires. The bi-stable molecule is switchable between two states upon application of a voltage along a selected pair of wires.
There is at present no known or published solution for addressing molecular scale devices and getting information into or out of a molecular system such that it can be read or accessed by a much larger system, for instance, CMOS. All present solutions for connection end up making the molecular scale devices spread out on a scale comparable with available lithography or direct writing capability. A "wagon wheel" strategy, for example, does this, where nano-scale wires are formed, fanning out from a central "spoke". The overlap of two such adjacent "wagon wheels" forms intersecting junctions where each pair of wires cross to form a molecular wire crossbar. When all of the wires in the molecular wire crossbar must spread out, however, the total size of the system, including input/output (I/O), becomes comparable with the area of a lithographically formed system, and thus much of the size advantage of a molecular scale system is lost.
Thus, there remains a need for getting information into and out of a nanometer-scale molecular wire crossbar, also known as a chemically assembled electronic nanocomputer.